This invention relates generally to an automatic actuator system for a cooling fan of an internal combustion engine mounted on large-sized vehicles.
Generally, in water-cooled internal combustion engines mounted on vehicles, heat removal from the cooling water which has cooled the engine has been made by means of a radiator and a cooling fan directly driven by the engine. Therefore, the conventional engine cooling system has been disadvantageous in that the cooling fan is driven even when the engine is being warmed up immediately after it is started; that is; when cooling of the engine is unnecessary or even when the engine is run under cold condition and/or in cold regions thus consuming the output of the engine wastefully. In order to eliminate such a disadvantage, there has been proposed such an arrangement that the cooling water temperature is detected and, when the temperature thus detected exceeds a preset temperature, a cooling fan is driven by means of a hydraulic motor or an electric motor. However, because the control of the engine's cooling in such arrangement is carried out by on-off action, it has been impossible to obtain a satisfactory effect on reducing wastefulness of the engine output in case of large-sized vehicles.